Multiple-optical-axis photoelectric switches comprise a light emitter having a plurality of light emitting elements aligned and a light receiver having a plurality of light receiving elements aligned and paired with the light emitting elements respectively. Typically both units are disposed opposite to each other with a predetermined detecting region interposed therebetween. When an object is present between the light emitter and receiver, light emitted by the light emitter and traveling toward the light receiver is intercepted by the object. As a result, the amount of light received by the light receiver is reduced as compared with the case where no object is present. Accordingly, an object passing through the detecting region can be detected by measuring the amount of light received by the light receiver.
Main cases for the respective light emitter and receiver in this type of multiple-optical-axis photoelectric switch are disclosed in JP-10-74433-A (hereinafter referred to as “document 1”) and JP-U-2554755-B (hereinafter referred to as “document 2”). As disclosed, each main case is mounted to a mounting wall by a pair of mounting plates provided on both ends thereof and having an L-shaped cross section so as to pivot about a pivot shaft extending along the direction of alignment of the elements. Consequently, while each main case is mounted on the mounting wall, an optical axis can be adjusted so that the light emitted by each light emitter is received by the corresponding light receiver.
The mounting structure will be explained concretely with the structure of the document 1 exemplified. The aforesaid L-shaped mounting plate includes one of walls of the L-shaped mounting plate disposed opposite an end face of the main case, identified as the end face wall. The end face wall of the mounting plate is formed with an insertion hole and an arc groove having the insertion hole as its center, both extending through the end face wall. The other wall of the mounting plate is disposed opposite the mounting wall and is formed with a pair of through holes through which fixing screws are inserted to be threadingly engaged with the mounting wall. Mounting screws are inserted from an upper face of the end face wall, through the insertion hole and the groove, to be threadingly engaged with screw holes formed in the end of the main case respectively. Fixing screws are inserted through the paired insertion holes of the other wall and are threadingly engaged with screw holes of the mounting wall respectively, whereby the main case is fixed to the fixing wall. In the adjustment of optical axis, the mounting screw inserted through the groove of the end face wall is loosened such that the main case is capable of pivoting about the insertion hole. Upon completion of the optical axis adjustment, the mounting screw is retightened so that the position of the optical axis is fixed.
The multiple-optical-axis photoelectric switch is installed in various mounting places. There is sometimes a case where a sufficient space cannot be ensured above or below the main case. In this case, the loosening and tightening of the mounting screws provided on the end of the main case with a suitable tool are difficult during the optical axis adjustment of the aforesaid documents 1 and 2. As a result, there can be a case where the fixing screws are detached so that the main case is detached from the mounting wall in order to adjust the optical axis.
The present invention was made in view of the foregoing and an object thereof is to provide a multiple-optical-axis photoelectric switch in which the optical axis can be adjusted without being influenced by the limitation in the spaces above and below the main case when the multiple-optical-axis photoelectric switch is mounted at a predetermined mounting part.